Issued  June  22,  1910. 

U.  S.  DEPARTMENT  OF  AGRICULTURE. 


FARMERS’  BULLETIN  401. 


THE  PROTECTION  OF  ORCHARDS  IN  THE 
PACIFIC  NORTHWEST  FROM  SPRING 
FROSTS  BY  MEANS  OF  FIRES 
AND  SMUDGES. 


i\  j.  <  >’( 

Scientific  Assistant ,  Fruit-Disease  Investigations , 
Bureau  of  Plant  Industry . 


WASHINGTON: 
GOVERNMENT  P R I N T I  N G  O F  FIVE, 

1910. 


LETTER  OF  TRANSMITTAL. 


U.  S.  Department  of  Agriculture, 

Bureau  of  Plant  Industry, 

Office  of  the  Chief, 
Washington ,  D.  C. ,  March  16,  1910. 

Sir:  I  have  the  honor  to  transmit  and  to  recommend  for  publica¬ 
tion  as  a  Farmers’  Bulletin  the  accompanying  manuscript,  entitled 
“The  Protection  of  Orchards  in  the  Pacific  Northwest  from  Spring 
Frosts  by  Means  of  Fires  and  Smudges,”  prepared  by  Mr.  P.  J.  O’Gara, 
Scientific  Assistant,  Fruit-Disease  Investigations. 

A  great  deal  of  interest  has  developed  in  the  last  two  or  three  years 
among  fruit  growers  in  the  subject  of  protecting  orchards  artificially 
from  frosts.  A  good  many  attempts  have  been  made,  particularly  in 
the  Rocky  Mountain  States  and  on  the  Pacific  coast,  in  both  decidu¬ 
ous  and  citrus  orchards  to  ward  off  the  frost  damage  by  fires.  At 
the  request  of  fruit  growers  in  the  Rogue  River  Valley,  where  he  has 
been  assisting  in  the  eradication  of  pear-blight,  Mr.  O’Gara  undertook 
to  help  in  solving  the  problem  of  frost  prevention.  Notwithstand¬ 
ing  the  favorable  results  obtained,  it  must  be  acknowledged  that  there 
is  still  considerable  doubt  as  to  the  possibility  under  varied  conditions 
of  warding  off  the  damage  from  frosts  by  fires,  and  also  some  question 
about  its  practicability  in  open  orchards.  Nevertheless,  it  is  thought 
desirable  to  publish  Mr.  O’Gara’s  experiments  and  notes  on  this  sub¬ 
ject  at  the  present  time. 

Respectfully,  G.  H.  Powell, 

A  ding  Chief  of  Bureau . 

Hon.  James  Wilson, 

Secretary  of  Agriculture. 

2 

401 


CONTENTS. 


Page. 


Introduction .  5 

Preparation  necessary  for  frost  prevention .  G 

Materials  to  be  used  for  fuel .  7 

Materials  for  starting  fires .  9 

Manner  of  distributing  the  materials  in  the  orchard .  10 

Quantity  of  material  to  be  used  for  each  fire .  11 

Cost  of  materials  for  firing  an  acre .  12 

Necessity  of  understanding  weather  conditions .  13 

Meteorological  data  obtained  in  the  Rogue  River  Valley .  17 

Weather  conditions  producing  spring  frosts  in  the  Rogue  River  Valley .  19 

Injurious  temperatures .  20 

Results  of  the  work .  20 

Value  of  firing  the  orchards  when  the  cost  is  compared  with  the  value  of  the 

crop .  21 

Practical  suggestions  on  the  use  of  the  psychrometer  and  other  meteorological 

instruments .  22 

Conclusions .  24 

3 

401 


ILLUSTRATIONS. 


Page. 


Fig.  1.  Old  fence  rails  used  successfully  for  firing  in  saving  the  Bartlett  pear 

crop  of  Mr.  J.  G.  Gore  in  the  Rogue  River  Valley,  Oregon .  6 

2.  Old  rails  used  for  firing  to  save  the  crop  of  the  7-year-old  apple  orchard 

of  Mr.  J.  G.  Gore  in  the  Rogue  River  Valley,  Oregon .  7 

3.  View  in  the  Hollywood  Orchards,  Medford,  Oreg.,  at  5  a.  m.,  April  21, 

1909,  showing  the  smudging  used  to  prevent  frost  injury .  8 

4.  Paper  sacks  filled  with  shavings  and  sawdust  saturated  with  crude  fuel 

oil .  9 

5.  A  supply  of  paper  sacks  filled  with  shavings  and  saturated  with  crude 

fuel  oil  to  be  used  for  starting  fires .  9 

6.  Arrangement  of  cord  wood  in  the  Yellow  Newtown  apple  orchard  of  Mr. 

W.  Id.  Brown  in  the  Rogue  River  Valley,  Oregon .  10 

7.  Arrangement  of  cordwood  in  the  Esopus  orchard  of  Mr.  W.  II.  Brown 

in  the  Rogue  River  Valley,  Oregon .  11 

8.  Arrangement  of  material  on  the  outside  borders  of  the  pear  orchard  of 

Mr.  A.  C.  Allen  in  the  Rogue  River  Valley,  Oregon .  12 

9.  Fir  cordwood  with  dry  prunings  used  for  firing  in  the  apple  orchard  of 

Mr.  W.  H.  Brown  in  the  Rogue  River  Valley,  Oregon .  13 

10.  A  homemade  psychrometer  showing  the  wet  bulb  extending  below  the 

frame,  protected  by  a  heavy  wire  loop .  16 

11.  Side  view  of  a  homemade  psychrometer  showing  backs  soldered  to¬ 

gether 


401 

4 


1G 


B  P  I  .—505. 


THE  PROTECTION  OE  ORCHARDS  IN  THE  PACIFIC 
NORTHWEST  FROM  SPRING  FROSTS  BY  MEANS 
OF  FIRES  AND  SMUDGES. 


INTRODUCTION. 

The  object  of  this  bulletin  is  to  give,  in  considerable  detail,  the 
results  of  successful  experiments  and  the  methods  employed  in  pre¬ 
venting  frost  injury  by  means  of  fires  and  smudges  in  the  apple, 
peach,  and  pear  orchards  of  the  Rogue  River  Valley  in  southern 
Oregon  during  the  spring  of  1909. 

This  work  was  taken  up  by  the  writer  at  the  earnest  request  of 
several  growers,  whose  hearty  cooperation  made  it  possible  to  secure 
data  of  much  value.  It  is  believed  that  while  every  locality  has  its 
own  peculiar  factors  and  conditions,  the  results  obtained  in  the 
Rogue  River  Valley  will  be  of  more  or  less  interest  generally.  The 
practicability  of  protecting  orchards  from  frost  injury  has  remained 
more  or  less  an  open  question.  The  preventable  annual  losses  through¬ 
out  the  country  from  low  temperatures  during  the  blooming  period 
and  for  some  time  thereafter  amount  to  millions  of  dollars.  This  is 
no  doubt  due  to  the  facts  that  sufficient  practical  data  and  actual 
orchard  experience  which  would  serve  as  a  guide  for  the  fruit  grower 
are  wanting. 

The  excellent  work  done  by  the  Riverside  Horticultural  Club,"  of 
Riverside,  Cal.,  during  the  winter  of  1897  and  1898  brought  out 
many  facts  concerning  frost  prevention,  but  much  of  the  apparatus 
used  and  many  of  the  methods  employed  can  not  be  adopted  gen- 

erally. 

The  important  facts  to  be  known  by  the  grower  arc  how  to  prepare 
for  frost  prevention,  what  materials  to  employ  for  fuel  and  the  man¬ 
ner  of  distributing  them  in  the  orchards,  what  to  use  in  starting  the' 
fires  and  the  method  of  preparing  them,  etc. 

a  Farmers’  Bulletin  104,  U.  S.  Dept,  of  Agriculture,  entitled  Xoios  on  I  ro.n . 


401 


6 


PROTECTION  OF  ORCHARDS  FROM  SPRING  FROSTS. 


PREPARATION  NECESSARY  FOR  FROST  PREVENTION. 

It  should  be  understood  at  the  outset  that  frost  prevention  requires 
considerable  preparation.  It  is  impossible  to  get  the  material  for 
fuel  on  the  ground  and  have  it  distributed,  especially  where  the 
orchards  are  large,  after  frost  warnings  are  given  out,  since  these 
warnings  can  not  be  given  sufficiently  in  advance  of  the  time  necessary 
for  firing  in  the  orchards.  Whatever  the  material  to  be  used  may 
be,  it  should  be  so  placed  that  it  may  be  readily  distributed,  and  a 
sufficient  quantity  of  it  should  be  on  hand  in  case  it  may  become 
necessary  to  fire  for  a  considerable  length  of  time  or  in  case  several 


Fig.  1. — Old  fence  rails  used  successfully  for  firing  in  saving  the  Bartlett  pear  crop  of  Mr.  J.  G.  (lore  in  the 

Rogue  River  Valley,  Oregon. 


firings  are  required  during  the  season.  Usually  it  is  never  necessary 
to  fire  more  than  once  or  twice  during  the  season,  but  during  certain 
seasons  it  may  become  necessary  to  fire  four  or  five  times. 

The  material  for  building  these  fires,  especially  where  brush  and 
wood  are  to  be  the  fuel  used,  should  be  piled  up  along  the  side  of  the 
field  and,  if  necessary,  covered  to  keep  it  dry  so  that  it  will  ignite 
readilv.  This  work  may  be  done  at  anv  time  during  the  summer 
or  winter,  whenever  there  is  any  spare  time.  Usually  there  are 
times  when  this  work  can  be  done  without  any  real  loss  of  time, 

401 


PROTECTION  OP  ORCHARDS  FROM  SPRING  FROSTS.  7 

since  the  men  may  not  be  able  to  do  anything  else  with  profit  \t 
any  rate,  one  should  have  a  plentiful  supply  of  fuel  on  hand  and  bo 
sure  that  it,  is  near  by  where  it  can  be  readily  distributed  and  that 
it  is  in  a  dry  condition  so  that  it  can  be  readily  ignited.  The  writer 
has  known  of  failures  in  firing  where  the  grower  failed  to  keep  his 
material  in  shape  for  immediate  use. 


MATERIALS  TO  BE  USED  FOR  FUEL. 


The  materials  which  may  be  used  for  fuel  depend  largely  upon 
local  conditions.  In  some  places  the  use  of  wood  may  be  entirely 
out  of  the  question.  However,  there  is  a  choice  in  the  use  of  coal, 
crude  oil,  straw,  stable  manure,  or  any  rubbish  which  usually  accu- 


Fig.  2.— Old  rails  used  for  firing  to  save  the  crop  of  the  7-year  old  apple  orchard  of  Mr.  J.  G.  Gore  in  the 

Rogue  River  Valley,  Oregon. 


mulates  around  the  farm.  In  the  experiments  in  the  Rogue  River 
Valley,  while  there  was  some  variety  in  the  matter  of  fuel,  wood  was 
principally  used.  In  some  cases  good  fir  and  even  oak  cordwood 
was  used.  In  other  cases  old  rails  from  fences  which  had  been  torn 
down,  small  brush  wood,  and  even  primings  from  the  orchard  were 
used.  In  the  Bartlett  pear  orchard  of  Mr.  J.  G.  Gore  the  crops  were 
saved  for  two  years  in  succession  by  the  use  of  old  fence  rails,  as  illus¬ 
trated  in  figure  1.  Old  rails  were  also  successfully  used  in  saving  the 
crop  of  a  7-year-old  apple  orchard  (see  fig.  2).  There  are  usually  not 
enough  primings  in  any  one  orchard  to  be  worth  anything  except  lor 
use  in  starting  the  fires  quickly,  for  which  purpose  they  are  valuable 
if  kept  very  dry. 

401 


8  PROTECTION  OE  ORCHARDS  FROM  SPRING  FROSTS. 

Crude  oil  was  used  only  to  a  very  limited  extent.  The  Southern 
Pacific  Company  very  kindly  gave  a  considerable  quantity  of  their 
crude  locomotive-fuel  oil  from  their  tanks  at  Ashland,  Oreg.,  to  the 
growers  for  experimental  use.  It  was  found,  however,  that  since 
this  oil  contains  a  considerable  quantity  of  water,  due  to  the  fact 
that  it  is  pumped  from  the  oil  fields  through  pipes  having  a  water 
jacket,  it  is  very  hard  to  ignite  and  even  after  igniting  fails  to  burn 
well.  This  oil  was  used  in  different  kinds  of  pots  and  burners  with 
about  equal  success.  In  most  cases  the  fires  went  out  shortly  after 
lighting  or  the  contents  exploded  in  the  pots.  Although  the  crude 
oil  could  not  be  used  as  a  fuel,  it  was  found  very  valuable  for  satu- 


Fig.  3.— View  in  the  Hollywood  orchards,  Medford,  Oreg.,  at  5  a.  in.,  April  21,  1909,  showing  the  smudging 

used  to  prevent  frost  injury. 


rating  shavings  or  other  fine  materials  which  were  used  in  starting 
the  fires.  This  will  be  considered  in  detail  later. 

Stable  manure,  straw,  and  rubbish  were  also  employed,  but  only 
to  a  very  limited  extent.  These  materials  were  principally  used  for 
producing  a  dense  smudge,  with  the  idea  of  protecting  the  orchards 
from  the  direct  rays  of  the  sun  in  the  early  morning  after  it  was 
known  that  there  had  been  some  freezing  of  the  blossoms.  The  idea 
in  nearly  every  case  was  not  to  raise  the  temperature  of  the  air  in  the 
orchards,  as  was  the  case  with  the  use  of  wood,  but  simply  to  form  a 
heavy  smoke  blanket  which  would  prevent  the  blossoms  from  warm¬ 
ing  up  too  rapidly  in  case  they  were  slightly  frozen.  Figure  3  repre¬ 
sents  the  smudging  employed  in  the  Hollywood  orchards,  Medford, 
Oreg.,  at  5  o’clock  in  the  morning  on  April  21,  1909. 

Another  valuable  material  which  was  used  only  in  a  few  cases  is 
the  lignite  coal  which  is  mined  near  Medford.  This  coal,  although 

401 


PROTECTION  OF  ORCHARDS  FROM  SPRING  FROSTS 


not  igniting  very  readily,  was  found  to  be  of  considerable  value  if 
used  in  connection  with  wood.  In  using  the  coal  it  was  usually 

placed  on  top  of  the  wood  piles  and  was  found  to  bo  a  good 
heat  producer.  Un¬ 
doubtedly  it  will  be 
found  very  valuable 
where  fires  must  be 
prolonged  for  some 
time  during  very  cold 


nights. 


MATERIALS  FOR 
STARTING  FIRES. 


Fig.  4.— Paper  sacks  filled  with  shavings  and  sawdust  saturated 

with  crude  fuel  oil. 


In  the  experiments 
conducted  by  the  writer 
the  materials  used  for 
starting  the  fires  va¬ 
ried  about  as  widely  as 
the  materials  used  in 
maintaining  the  fires. 

These  materials  consisted  of  shavings  or  mill  planings,  sawdust, 
straw,  crude  oil,  light  brush,  and  rubbish  or  rakings  from  the  adjoin¬ 
ing  woods.  One  of  the  best  materials  was  found  to  be  mill  planings, 

which  were  put  into 
medium  -  sized  p  a  p  e  r 
sacks  and  the  whole 
saturated  with  crude 
oil  or  kerosene.  A  con¬ 
siderable  n  u  m  b  e  r  of 
these  bags  were  pre¬ 
pared  beforehand  and 
kept  in  a  shed,  where 
they  were  readily  avail¬ 
able  when  it  was  nec¬ 
essary  to  build  the  fires. 
Sawdust  mingled  with 
tar  was  also  used,  but  it 
was  found  to  be  harder 
to  handle  and  not  so 
easily  made  up  as  the 

bags  of  shavings.  Figures  4  and  5  show  the  bags  used  in  starting 
the  fires.  Pine  leaves  and  other  forest  leaves  may  be  used  fur  tins 

purpose. 

38302— Bui.  401—10 - 2 


Fig.  5. — A  supply  of  paper  sacks  filled  with  shavings  and  saturated 
with  crude  fuel  oil  to  be  used  for  starting  fires. 


10 


PROTECTION  OF  ORCHARDS  FROM  SPRING  FROSTS. 


In  some  cases,  instead  of  using  shavings  or  very  light  material  of 
any  kind,  kerosene  was  poured  directly  on  the  coarse  material  and 
then  ignited  with  a  match  or  a  torch.  This  method,  however,  is 
more  expensive  than  the  former,  and  unless  the  wood  or  other  mate¬ 
rial  is  very  dry  the  fires  will  not  start.  One  of  the  most  important 
factors  in  firing  is  to  get  the  fires  lighted  as  rapidly  as  possible  when 
the  temperature  begins  to  drop  or  approaches  the  danger  point.  Of 
course  where  there  is  only  a  small  acreage  this  is  not  quite  so  urgent 
as  where  there  is  a  considerable  amount  of  ground  to  be  gone  over. 
With  the  use  of  kerosene  torches  and  with  the  fires  already  laid,  it 
was  found  that  the  fires  for  an  acre  could  be  lighted  by  one  man  in 
from  seven  to  ten  minutes.  The  use  of  a  kerosene  or  gasoline  torch 


Fig.  G.— Arrangement  of  cord  wood  in  the  Yellow  Newtown  apple  orchard  of  Mr.  W.  II.  Brown  in  the  Rogue 

River  Valley,  Oregon. 


is  advisable  for  the  reason  that  it  does  not  readily  blow  out.  With 
such  a  device  one  can  light  the  fires  almost  as  rapidly  as  he  can  run. 

MANNER  OF  DISTRIBUTING  THE  MATERIALS  IN  THE  ORCHARD. 

The  number  of  heaps  or  piles  of  material  which  should  be  distrib¬ 
uted  in  the  orchard  will  vary  somewhat,  depending  upon  the  kind  of 
material  used,  about  forty  to  fifty  piles  per  acre  being  usually  sufli- 
cient.  In  most  cases  a  heap  or  pile  was  placed  between  every  four 
trees — that  is  to  say,  a  pile  every  other  tree  row  in  each  direction  in 
the  orchard.  The  arrangement  of  cord  wood  in  the  apple  orchard  of 
Mr.  W.  H.  Brown  is  shown  in  figure  6.  Figure  7  illustrates  a  simi¬ 
lar  arrangement  in  an  Esopus  (S  pitzenberg)  apple  orchard.  Gener¬ 
al 


PROTECTION  OF  ORCHARDS  FROM  SPRING  FROSTS.  ]  ] 

ally  it  will  be  found  that  only  half  of  these  heaps  will  have  to  be 
lighted  at  one  time,  which  of  course  allows  a  large  amount  of  reserve 
material  that  may  be  used  in  case  it  is  impossible  to  keep  the  temper¬ 
ature  up  with  only  half  the  fires  lighted. 

It  is  also  well  to  place  heaps  of  fuel  on  the  outer  edges  or  borders 
of  the  orchard,  since  it  is  olten  found  that  the  outside  trees  may  suffer 
where  a  slight  bieeze  tends  to  blow  the  heat  away.  These  piles 
should  be  distributed  outside  the  last  row  of  the  orchard,  and  in  ease 
the  temperature  can  not  be  kept  up  they  should  be  lighted.  Figure  8 
shows  the  distribution  of  piles  on  the  outside  borders  of  the  pear 
orchard  of  Mr.  A.  C.  Allen,  Medford,  Oreg. 

In  case  the  temperature  can  not  be  kept  up  to  28°  F.,  a  certain 


Fig.  7. — Arrangement  of  cordwood  in  the  Esopus  orchard  of  Mr.  W.  H.  Brown  in  the  Rogue  River  Valley, 

Oregon. 


amount  of  straw  or  stable  manure,  which  will  produce  a  dense  smudge, 
should  be  placed  upon  these  heaps  before  the  sun  rises  in  order  to 
prevent  the  slightly  frozen  fruit  or  blossoms  from  thawing  out  too 
rapidly.  These  smudges  should  be  started  on  the  side  or  sides  from 
which  the  wind  is  blowing  and  the  material  should  be  wet,  so  as  to 
make  it  burn  without  any  flame. 

QUANTITY  OF  MATERIAL  TO  BE  USED  FOR  EACH  FIRE. 


Experience  has  shown  that  the  fires  should  not  he  large,  since 
large  fires  tend  to  produce  convective  currents  that  are  apt  to  bring 
in  cold  air;  hence,  the  quantity  of  material  for  each  heap  need  not 
be  very  great.  Large  fires  also  might  scorch  the  blossoms. 

401 


12 


PROTECTION  OF  ORCHARDS  FROM  SPRING  FROSTS. 


four  to  five  pieces  of  cordwood,  or  its  equivalent  in  any  other  kind  of 
wood  or  old  rails,  are  sufficient  for  a  single  fire;  very  often  when  the 
low  temperature  is  of  short  duration  all  of  this  material  will  not  be 
consumed  in  a  single  firing.  Figure  9  shows  the  piles  of  fir  cordwood 
with  dry  prunings  used  in  firing  the  apple  orchard  of  Mr.  W.  If.  Brown. 
In  case  stable  manure  or  rubbish  was  used  a  larger  number  of  heaps 
were  placed,  and  the  quantity  of  material  to  each  heap  averaged  about 
a  bushel  or  a  bushel  and  a  half. 


Fig.  8. — Arrangement  of  material  on  the  outside  borders  of  the  pear  orchard  of  Mr.  A.  C.  Allen  in  the  Rogue 

River  Valley,  Oregon. 

COST  OF  MATERIALS  FOR  FIRING  AN  ACRE. 

The  cost  of  the  material  for  firing  varied  greatly,  depending  upon 
how  it  was  obtained.  In  some  cases  where  good  cordwood  was  used 
the  cost  of  one  firing  was  given  as  $2  per  acre.  Mr.  W.  II.  Brown, 
who  used  good  fir  cordwood,  states  that  when  using  from  five  to 
seven  sticks  in  a  pile  every  second  row  one  way  and  every  fourth 
row  the  other  the  cost  per  acre  for  three  hours’  firing  approximated 
60  cents.  However,  it  may  be  stated  that  generally  the  cost  per 
acre  for  one  night  was  between  $2  and  $2.50.  In  some  cases  the 
cost  was  estimated  as  high  as  $4,  but  it  is  quite  possible  that  more 
material  than  was  necessary  was  burned  and  that  a  higher  price  than 
usual  was  paid  for  it.  Where  stable  manure  and  rubbish  alone  were 
used  the  cost  for  firing  per  acre  was  from  4  to  10  cents.  This  was 
because  the  material  was  on  hand  and  the  only  element  of  expense 
was  for  distributing  it. 


401 


PROTECTION  OF  ORCHARDS  FROM  SPRING  FROSTS. 


13 


The  cost  of  labor  for  firing  an  acre  also  varied,  but  a  good  general 
average  would  be  about  SI.  Of  course  this  item  of  expense  varied 
with  the  type  of  material  used  as  well  as  with  the  distance  that  it 
was  necessary  to  haul  it. 


NECESSITY  OF  UNDERSTANDING  WEATHER  CONDITIONS. 


Before  efficient  work  can  be  done  in  frost  prevention  a  thorough 
understanding  of  local  weather  conditions  must  be  had.  In  other 
words,  the  grower  should  know  when  to  smudge  or  fire  in  the  orchards. 
Unless  he  knows  beforehand  that  freezing  temperatures  may  be  ex¬ 
pected,  the  opportunity  for  firing  at  the  right  time  may  be  lost. 


Fig.  9. —Fir  cordwood  with  dry  prunings  used  for  firing  in  the  apple  orchard  of  Mr.  W.  II.  Brown  in  the 

Rogue  River  Valley,  Oregon. 

Again,  unless  he  is  reasonably  certain  low  temperatures  will  occur 
during  the  night,  he  may  waste  a  considerable  quantity  of  costly 
material  when  there  would  be  no  real  need  of  it. 

In  order  to  carry  on  the  work  of  frost  prevention  successfully,  daily 
weather  reports  or  the  weather  map,  preferably  both,  should 
available.  In  many  localities  the  use  of  a  weather  map  would  be 
out  of  the  question,  since  it  may  be  at  least  twenty-four  hours  old 
and  of  very  little  value  when  it  is  received.  Especially  on  the 
Pacific  coast  there  is  very  little  gained  by  using  a  map  that  is  so  old. 
In  case  the  map  can  not  be  used,  telegraphic 'reports  should  be 
received  every  day.  During  the  time  that  the  writer  was  at  voik 
on  frost  prevention  in  the  Pogue  Piver  \  alley,  weather  maps  ve:e 

401 


14 


PROTECTION  OF  ORCHARDS  FROM  SPRING  FROSTS. 


received  from  the  Weather  Bureau  station  at  Sacramento,  Cal., 
through  the  kindness  of  Mr.  N.  B.  Taylor,  observer.  Air.  Taylor 
also  gave  valuable  advice  in  regard  to  conditions  on  the  Pacific 
coast,  especially  in  the  small,  inclosed  valleys  which  are  sur¬ 
rounded  by  high  mountains.  The  Weather  Bureau  office  at  Port- 
land,  Oreg.,  kindly  furnished  telegraphic  reports  to  the  Medford 
Commercial  Club,  and  weather  signals  were  hoisted.  The  assistance 
from  both  of  these  Weather  Bureau  offices  was  of  the  greatest  impor¬ 
tance  in  carrying  out  the  work  successfully. 

Of  equal  importance  with  the  general  forecasts  given  by  the  Sac¬ 
ramento  and  Portland  stations  were  the  local  observations  and  fore¬ 
casts  of  the  writer,  made  necessarv  by  the  absence  of  a  Weather 
Bureau  observer.  In  a  valley  situated  as  is  the  Pogue  Biver  Valley, 
local  conditions  and  surroundings  influence  to  a  considerable  degree 
the  temperature,  air  currents,  relative  humidity,  etc.  It  was  found 
that  the  most  important  thing  to  the  grower  was  the  immediate  local 
forecast  made  every  evening  about  sundown.  An  inspection  of  the 
record  of  observations  made  at  Medford,  Oreg.,  during  the  months 
of  April  and  May,  1909,  as  presented  in  the  following  table,  will  show 
the  nature  of  this  work: 


Table  I. — Record  of  weather  observations  at  Medford ,  Oreg.,  during  April  and  May,  1009. 
Readings  referred  to  psy  chrome  trie  tables  for  a  barometric  pressure  of  29  inches. 


Wind. 


Date. 

Timeoi 

obser¬ 

vation. 

Sky. 

Direction. 

Velocity. 

1909. 

Apr.  9 

P.  M. 

7.  45 

Partly  cloudy. . . 

NE. 

Slight... 

9 

9.  10 

Clearing . 

NE. 

Calming 

10 

8.  00 

Clear . 

Calm.. . . 

10 

10.  00 

...  .do . 

. .  .do . 

11 

7.  25 

_  do . . 

...do.... 

11 

9.  00 

.do. . 

. .  .do . 

12 

9.  45 

. do . 

NE. 

Slight... 

13 

7.  00 

. do . 

NE. 

. .  .do . 

13 

10.  00 

. do . 

Calm.. . . 

14 

7.  15 

. do . 

NE. 

Slight... 

14 

9.  45 

. do . 

Calm.. . . 

17 

8.  45 

. do . 

. .  .do . 

17 

9.  30 

. do . 

...do . 

18 

6.  30 

Partly  cloudy.  . 

N. 

Slight. . . 

18 

8.  30 

. do . 

N. 

.  ..do . 

18 

9.  30 

Clear . 

Calm.. . . 

19 

6.  45 

Hazy . 

N. 

Slight... 

19 

8.  30 

Clear . 

Calm.. . . 

19 

9.  00 

. do . 

...do..  .. 

20 

7.30 

. do . . . 

N. 

Slight. . . 

20 

9.  00 

. do. . . 

N. 

...do . 

21 

7.  30 

. do . 

Calm.. 

21 

9.  15 

. do . 

. .  .do . 

22 

7.00 

Hazy . 

NE. 

Slight. . . 

22 

8.  00 

Clear . 

Calm. . 

22 

10.00 

Ps 

jQ 

3 

rQ 

b 

a 

ychr 

read 

A 

3 

o> 

ome 

mgs. 

aJ 

O 

a 

CL) 

<D 

5 

ter 

4-1 

.2 

*o 

ft 

1 

<D 

ft 

Lowest  temperature 
observed  during 
the  night. 

Remarks. 

°F. 

°P. 

°  F. 

°F. 

°F. 

59 

45 

14 

28 

Serious  injury  on  un- 

55 

41 

14 

21 

20 

smudged  orchards. 

45 

40 

5 

34 

Heavy  white  frost,  but 

40 

36 

4 

31 

28 

no  injury. 

56 

46 

10 

35 

53 

44 

9 

34 

31 

55 

47 

8 

39 

36 

61 

49 

12 

37 

51 

45 

6 

39 

37 

60 

46 

14 

31 

48 

42 

6 

35 

33 

56 

46 

10 

35 

49 

43 

6 

36 

33 

59 

46 

13 

31 

. 

Clouded  about  mid- 

54 

41 

13 

23 

night,  hence  no  frost 

50 

38 

12 

19 

28 

injury. 

56 

44 

12 

29 

Moderate  white  frost — 

50 

42 

8 

32 

no  injury. 

49 

41 

8 

31 

29 

54 

43 

11 

29 

Frost  injury  in  un- 

49 

40 

9 

28 

26 

smudged  orchards. 

60 

48 

12 

35 

51 

43 

8 

34 

30 

63 

47 

16 

28 

Do. 

58 

45 

13 

29 

52 

42 

10 

29 

26 

401 


PROTECTION  OF  ORCHARDS  FROM  SPRING  FROSTS 


15 


Table  I. — Record  of  weather  observations  at  Medford ,  Oreg during 
Readings  referred  to  psy  chrome  trie  tables  for  a  barometric  pressure' of 


Date. 

Time  of 
obser¬ 
vation. 

Sky. 

Wind. 

Tsychrometer 

readings. 

Lowest  temperature 
observed  during 
the  night. 

Direction. 

Velocity. 

Dry  bulb. 

Wet  bulb. 

Difference. 

Dew-point. 

1909. 

r.  m 

°  F. 

°  F. 

°F. 

°  F. 

°  F. 

Apr.  23 

8.  00 

Clear . 

Calm. . . . 

53 

43 

10 

31 

23 

9.  00 

. do . 

. .  .do _ 

50 

42 

Q 

29 

24 

7.00 

Slightly  cloudy.. 

. .  .do . 

69 

14 

43 

24 

8.  15 

. do . 

. .  .do . 

60 

51 

q 

43 

40 

25 

7.  30 

Tartly  cloudy. . . 

NE. 

Slight... 

69 

56 

13 

46 

43 

26 

7.  20 

. do . 

NE. 

...do . 

66 

56 

10 

48 

46 

27 

7.  20 

. do . 

NE. 

...do . 

54 

47 

7 

40 

27 

8. 15 

. do . 

NE. 

. .  .do . 

52 

45 

7 

37 

27 

9.  00 

Clearing . 

NE. 

Brisk. . . 

50 

43 

7 

35 

34 

28 

7.  15 

Clear . 

NE. 

. .  .do . 

55 

45 

10 

34 

28 

8.  00 

. do . 

NE. 

Slight. . . 

52 

44 

8 

28 

9.  00 

. do . 

Calm.. . . 

52 

43 

9 

32 

29 

29 

7.  15 

. do . 

NE. 

Slight. . . 

60 

48 

12 

35 

29 

8.  15 

. do . 

Cairn.. . . 

54 

47 

7 

40 

29 

9.  15 

. do . 

. .  .do . 

52 

46 

6 

40 

29 

10.  15 

. do . 

. .  .do . 

48 

44 

4 

40 

37 

30 

7.  15 

. do . 

NE. 

Slight. . . 

68 

56 

12 

47 

30 

8.  15 

. do . 

NE. 

. .  .do . 

63 

54 

9 

47 

45 

May  1 

8.  15 

. do . 

Calm.. . . 

66 

56 

10 

48 

46 

2 

8.  15 

. do . 

. .  .do . 

68 

13 

44 

42 

3 

8.  15 

. do . 

. .  .do . 

67 

54 

13 

43 

40 

4 

8.  45 

Cloudy . 

NE. 

Slight... 

54 

44 

10 

32 

4 

9.  30 

Clearing . 

NE. 

.  ..do . 

52 

42 

10 

29 

25 

5 

7.  30 

Clear . 

NE. 

. .  .do . 

62 

50 

12 

38 

5 

8.  15 

. do . 

NE. 

. .  .do . 

59 

47 

12 

34 

5 

9.  00 

. do . 

Calm.. . . 

56 

46 

10 

35 

5 

9.  40 

. .  .do . . . 

...do . 

52 

44 

8 

35 

30 

6 

8.  15 

. ... .do. . . 

. .  .do . 

60 

50 

10 

41 

40 

7 

8.  15 

. do . 

NE. 

Slight. . . 

62 

48 

14 

32 

7 

9.  15 

. do . 

Calm.. . . 

54 

45 

9 

35 

32 

8 

8.  15 

Tartly  cloudy. . . 

NE. 

Slight... 

61 

48 

13 

34 

8 

9.  20 

. do . 

NW. 

...do . 

57 

46 

11 

34 

32 

9 

8.  00 

Cloudy.. . . 

W. 

. .  .do . 

51 

42 

9 

31 

9 

9.  00 

Tartly  cloudy. . . 

w. 

.  ..do . 

49 

41 

8 

31 

9 

10.  10 

Clearing . 

Calm.. . . 

47 

40 

7 

31 

29 

10 

7.  15 

Cloudy.... 

NE. 

Slight. . . 

54 

45 

9 

35 

10 

10.  00 

. do . 

NE. 

...do . 

50 

43 

7 

35 

33 

11 

7.30 

. do . 

NE. 

...do . 

53 

45 

8 

36 

11 

8.  15 

. do . 

NE. 

.  ..do . 

52 

45 

7 

37 

34 

12 

7.  45 

Clear. 

NE. 

.  .do . 

60 

49 

11 

38 

12 

9.  00 

. do . 

Calm.. . . 

54 

46 

8 

38 

35 

13 

8.  00 

.  .do. . 

. .  .do . 

62 

52 

10 

43 

13 

10.  00 

. do  ... 

. .  .do . 

52 

46 

6 

40 

37 

14 

7.  20 

Hazy . 

NE. 

Slight. . . 

61 

47 

14 

32 

32 

15 

8.  15 

Cloudy . 

Calm.. . . 

53 

48 

5 

43 

42 

16 

8.  00 

Tartly  cloudy. . . 

NE. 

Slight. .. 

58 

50 

8 

43 

41 

17 

8.  00 

Clear . 

NE. 

. . .do . 

58 

48 

10 

38 

36 

18 

8.  00 

. do . 

Calm.. . . 

61 

50 

11 

39 

36 

19 

8.  00 

do 

. .  .do . 

57 

48 

9 

39 

37 

20 

7.  45 

Cloudy . 

NE. 

Slight... 

55 

45 

10 

34 

32 

21 

8.  00 

Clear . 

Cairn.. . . 

55 

45 

10 

34 

32 

22 

8.  00 

.  .do. . 

.  ..do . 

56 

46 

10 

35 

32 

23 

8.  00 

...do . 

63 

52 

11 

42 

40 

24 

8.  00 

.do 

. .  .do . 

67 

55 

12 

45 

42 

25 

9.  15 

Cloudy.. 

. .  .do . 

69 

56 

13 

46 

45 

26 

9.  00 

Tartly  cloudy. 

.  ..do . 

62 

57 

5 

54 

50 

27 

8.  00 

Cloudy . 

N. 

Slight... 

55 

48 

7 

41 

39 

28 

8.  15 

. do . 

N. 

.  ..do . 

54 

50 

4 

47 

45 

29 

8.  15 

. do . 

N. 

.  ..do . 

62 

56 

6 

52 

49 

30 

9.  00 

Clear . 

Calm.. . . 

72 

63 

9 

59 

56 

31 

8.  30 

. do . 

.  ..do . 

76 

64 

12 

57 

54 

401 


ipril  and  May ,  1909. 
29  inches — Cont’d. 


Remarks. 


Moderate  white  frost- 
no  injury. 


Rain  most  of  day;  clear¬ 
ing  toward  9  p.  m.; 
clear  at  11  p.  m. 

Heavy  white  frost. 


Freezing  temperatures 
were  reached  about 
midnight.  In  one  or 
two  spots  23°  F.  was 
recorded.  Further  in¬ 
jury  in  unsmudged  or¬ 
chards. 


White  frost. 


Rained  nearly  all  day. 


Some  rain  during  day. 
Rain. 

Do. 

Do. 


16 


PROTECTION  OF  ORCHARDS  FROM  SPRING  FROSTS. 


In  some  cases  it  will  be  noticed  that  several  observations  were  made 
throughout  the  evening,  so  as  to  determine  the  trend  of  local  weather 
conditions.  The  most  important  observations  were  those  made  with 
the  psychrometer,  an  instrument  for  measuring  the  quantity  of  water 
vapor  in  the  atmosphere,  this  vapor  determining  to  a  very  great 
extent  whether  or  not  frost  may  be  expected.  The  psychrometer 
is  made  of  two  thermometers,  one  bulb  being  covered  with  a  piece  of 
thin  muslin  cloth  and  the  other  left  exposed  (see  fig.  10).  The  cov- 


Fig.  10. — A  homemade  psy¬ 
chrometer  showing  the 
wet  bulb  extending  be¬ 
low  the  frame,  protected 
by  a  heavy  wire  loop. 


Fig.  11. — Side  view  of  a 
homemade  psychrome¬ 
ter  showing  backs  sol¬ 
dered  together. 


ered  bulb  is  wet  and  the  instrument  whirled  rapidly  so  as  to  produce 
evaporation  from  the  wet  bulb.  The  temperatures  of  the  two  bulbs 
are  read  when  the  wet  bulb  has  reached  its  lowest  point  and  the  differ¬ 
ence  between  the  two  readings  taken.  These  readings  are  then  re¬ 
ferred  to  tables  published  by  the  United  States  Weather  Bureau 
showing  the  dew-point,  i.  e.,  the  temperature  at  which  dew  or  frost 
will  form,  a  reprint  of  which  follows: 

401 


PROTECTION  OP  ORCHARDS  FROM  SPRING  FROSTS. 


Table  II  —  For  determining  the  temperature  of  dew-point  in  degrees  Fahrenheit 


Dry- 

bulb 

ther- 

Dew-p 

oint  when  the  difference  between  the  wet-bulb  and  dry-bulb  temperatures  is 

mom- 

eter. 

1° 

2° 

3° 

4° 

5° 

6° 

7° 

8° 

9° 

10° 

11° 

12° 

13° 

14° 

15° 

°F. 

°F. 

°F. 

°F. 

°F. 

°F. 

°F. 

°F. 

°F. 

°F. 

°F. 

°F. 

°F 

0  F 

°  V 

35 _ 

33 

30 

28 

25 

22 

18 

14 

8 

1 

-8 

-28 

r . 

oO.  .  . 

Q7 

34 

31 

29 

26 

23 

20 

15 

11 

4 

-4 

-19 

O  /  .  .  . 

qq 

35 

32 

30 

27 

24 

21 

17 

13 

7 

-1 

-12 

-44 

OO  ... 

36 

33 

3 1 

28 

26 

23 

19 

14 

9 

3 

—  7 

-25 

o  y . . . 

37 

34 

32 

29 

27 

24 

21 

16 

12 

6 

-  3 

-16 

4U .  .  . 

38 

35 

33 

3 1 

28 

25 

22 

18 

14 

8 

1 

-10 

-35 

41 .  .  . 

39 

37 

34 

32 

29 

26 

23 

20 

16 

11 

4 

-  5 

-21 

4Z.  .  . 

40 

38 

35 

33 

30 

28 

25 

21 

17 

13 

7 

—  1 

—  13 

—59 

43 ... 

41 

39 

36 

34 

31 

29 

26 

23 

19 

15 

10 

3 

—  7 

— 98 

44 _ 

42 

40 

38 

35 

32 

30 

27 

24 

21 

17 

12 

6 

—  2 

—  17 

45. . . 

43 

41 

39 

36 

34 

31 

29 

26 

22 

19 

14 

8 

2 

—  9 

27 

46 _ 

44 

42 

40 

37 

35 

32 

30 

27 

24 

20 

16 

11 

5 

—  4 

9ft 

47... 

45 

43 

41 

39 

36 

34 

31 

28 

25 

22 

18 

13 

8 

0 

—  19 

48... 

46 

44 

42 

40 

37 

35 

32 

30 

27 

23 

20 

15 

10 

4 

—  6 

49. . . 

47 

45 

43 

41 

39 

36 

34 

31 

28 

25 

21 

17 

13 

7 

_  2 

50 _ 

48 

46 

44 

42 

40 

37 

35 

32 

29 

27 

23 

19 

15 

9 

2 

51 . . . 

49 

47 

45 

43 

41 

39 

36 

34 

31 

28 

25 

21 

17 

12 

6 

52 _ 

50 

48 

46 

44 

42 

40 

37 

35 

32 

29 

26 

23 

19 

14 

9 

53 _ 

51 

49 

47 

45 

43 

41 

39 

36 

34 

31 

28 

24 

21 

16 

11 

54 _ 

52 

50 

49 

47 

44 

42 

40 

38 

35 

32 

29 

26 

23 

19 

14 

55 _ 

53 

52 

50 

48 

46 

43 

41 

39 

36 

34 

31 

28 

24 

21 

16 

56 _ 

54 

53 

51 

49 

47 

45 

43 

40 

38 

35 

32 

29 

26 

23 

19 

57 _ 

55 

54 

52 

50 

48 

46 

44 

42 

39 

36 

34 

31 

28 

24 

21 

58 _ 

56 

55 

53 

51 

49 

47 

45 

43 

40 

38 

35 

32 

29 

26 

22 

59. . . 

57 

56 

54 

52 

50 

48 

46 

44 

42 

39 

37 

34 

31 

28 

24 

60... 

58 

57 

55 

53 

51 

49 

47 

45 

43 

41 

38 

35 

32 

29 

26 

61... 

59 

58 

56 

54 

52 

51 

49 

46 

44 

42 

39 

37 

34 

31 

28 

62... 

60 

59 

57 

55 

54 

52 

50 

48 

46 

43 

41 

38 

35 

32 

30 

63 . . . 

61 

60 

58 

56 

55 

53 

51 

49 

47 

45 

42 

40 

37 

34 

31 

64 _ 

62 

61 

59 

58 

56 

54 

52 

50 

48 

46 

44 

41 

38 

36 

33 

65 . . . 

63 

62 

60 

59 

57 

55 

53 

51 

49 

47 

45 

43 

40 

37 

34 

66 . . . 

64 

63 

61 

60 

58 

56 

54 

53 

51 

48 

46 

44 

42 

39 

36 

67... 

65 

64 

62 

61 

59 

57 

56 

54 

52 

50 

48 

45 

43 

40 

38 

68... 

67 

65 

63 

62 

60 

58 

57 

55 

53 

51 

49 

47 

44 

42 

39 

69... 

68 

66 

64 

63 

61 

60 

58 

56 

54 

52 

50 

48 

46 

43 

41 

70... 

69 

67 

66 

64 

62 

61 

59 

57 

55 

53 

51 

49 

47 

45 

42 

A  complete  description  of  the  psy  chrome  ter,  with  directions  for 
using  it,  was  given  in  the  Yearbook  of  the  United  States  Department 
of  Agriculture  for  1908  by  Mr.  Dewey  A.  Seeley,  in  a  paper  entitled 
“ Instruments  for  Making  Weather  Observations  on  the  Farm.” 
Other  instruments,  such  as  the  barometer,  rain  gauge,  and  ther¬ 
mometer,  and  their  uses  are  also  explained  in  this  article. 

METEOROLOGICAL  DATA  OBTAINED  IN  THE  ROGUE  RIVER 

VALLEY. 


It  is  well  known  to  meteorologists,  and  can  be  seen  upon  inspection 
of  Table  I,  that  there  is  a  very  close  relation  between  the  dew-point 
of  the  evening  and  the  minimum  temperature  of  the  night, 
instance,  at  9.10  p.  m.,  on  April  9,  the  dew-point  recorded  was  21°  I* . 
At  this  time  the  sky,  which  had  been  partly  clouded  early  in  the 
evening,  began  to  clear,  and  a  slight  wind  which ’had  been  blowing 
from  the  northeast  began  to  calm.  The  lowest  temperature  recorded 
before  morning  was  20°  F.  in  some  of  the  lowest  spots  throughout 
the  valley,  although  on  higher  ground  it  was  somewhat  above  that 
point.  Again,  on  April  13,  at  7  p.  m.,  with  a  clear  sky  and  the  wind 

401 


18 


PROTECTION  OF  ORCHARDS  FROM  SPRING  FROSTS. 


blowing  slightly  from  the  northeast,  the  dew-point  was  37°  F.  The 
minimum  temperature  recorded  during  the  night  was  37°  F. 

By  a  careful  inspection  of  the  last  two  columns  of  figures  in  Table  I 
it  will  be  seen  that  the  dew-point  recorded  in  the  evening  was  not 
far  at  any  time  from  the  lowest  temperature  recorded  during  the 
night  following.  In  one  instance  only,  and  that  on  April  18,  was 
there  a  rather  wide  divergence  from  this  general  rule.  By  referring 
to  the  table  it  may  be  seen  that  the  dew-point  at  9.30  p.  m.  was 
19°  F.,  and  the  minimum  temperature  recorded  during  the  night  was 
28°  F.  The  reason  for  this  was  that  the  sky  became  clouded  about 
midnight,  thus  preventing  further  radiation  of  heat  from  the  ground. 
The  warnings  given  out  on  this  particular  evening  were  based  on 
weather  conditions  reported  by  the  Portland  Weather  Bureau  sta¬ 
tion,  as  well  as  on  the  weather  map  which  had  been  received  from 
Sacramento,  Cal.  The  fruit  growers  were  advised  that  it  would  not 
be  necessary  to  build  fires  in  their  orchards,  as  it  was  very  likely 
that  the  sky  would  become  clouded  before  any  serious  lowering  of 
the  temperature  had  taken  place.  As  a  matter  of  fact  the  tempera¬ 
ture  recorded,  28°  F.,  lasted  only  a  very  short  time,  perhaps  not 
more  than  half  an  hour,  when  the  thermometer  again  began  to  rise. 
Table  I,  which  it  will  be  worth  while  looking  over  carefully,  is  self- 
explanatory.  The  method  of  keeping  such  records  is  not  very  diff- 
cult;  hence,  further  explanation  will  not  be  necessary. 

In  giving  out  weather  warnings  it  is  quite  important  that  there 
should  be  a  good  rural  telephone  system.  Local  conditions  often 
change  so  rapidly  that  warnings  may  have  to  be  modified  even 
during  the  course  of  an  afternoon  or  evening.  In  the  Rogue  River 
Valley  the  writer  was  particularly  fortunate  in  having  at  hand  the 
very  best  telephone  service.  While  all  of  the  growers  who  smudged 
did  not  have  telephones  of  their  own,  appointments  were  made 
whereby  several  of  them  might  get  the  weather  reports  from  a  neigh¬ 
bor  who  had  a  telephone.  The  area  covered  in  the  work  was  prob¬ 
ably  from  10  to  12  miles  or  more  each  way  from  the  town  of  Medford. 
In  two  or  three  instances,  by  request,  telephone  messages  were  sent 
to  a  distance  of  30  miles.  In  giving  out  the  warnings  it  was  usual 
to  indicate  as  nearly  as  possible  the  time  during  the  night  when  it 
would  be  necessary  to  start  the  smudge  fires.  This  was  important 
to  those  who  did  not  have  frost  alarms.  By  using  an  ordinary 
alarm  clock  they  were  awakened  at  the  hour  indicated  and  began 
the  work  of  smudging. 

The  frost  alarm  is  nothing  more  or  less  than  a  thermometer  which 
can  be  set  to  ring  an  electric  bell  at  a  given  temperature,  and  it  would 
be  advisable  for  those  who  may  need  to  smudge  to  have  one,  since  it 
often  saves  a  great  deal  of  time  and  worry  as  well  as  avoids  too 
much  loss  of  sleep. 

401 


PROTECTION  OF  ORCHARDS  FROM  SPRING  FROSTS. 


19 


WEATHER  CONDITIONS  PRODUCING  SPRING  FROSTS  IN  THE 

ROGUE  RIVER  VALLEY. 


During  the  spring  months  it  is  found  that  during  the  day  the  wind 
blows  mostly  from  the  north  or  northeast.  These  winds  are  not 
moisture  laden;  that  is  to  say,  the  relative  humidity  is  usually  very 
low,  often  as  low  as  25  per  cent.  During  the  night  when  frosts  are 
likely  to  occur  the  winds  die  down  altogether  or  begin  to  blow 
slightly  from  the  south.  The  winds  from  the  south  are  also  very  dry, 
and  may  even  tend  to  lower  the  dew-point  below  that  observed  in 
the  early  evening.  In  giving  out  the  warnings  this  factor  was  taken 
into  account.  By  referring  to  Table  I,  it  will  be  seen  that  the  lowest 
temperature  recorded  during  each  night  was  usually  somewhat  below 
the  dew-point  recorded  in  the  evening.  This  was  probably  due  to  the 
fact  that  the  south  winds  have  even  less  moisture  than  those  blowing 


from  the  north  or  northeast.  In  this  valley  whenever  the  winds 
blow  from  the  west  or  northwest  it  is  rare  that  frosts  occur,  since  there 
is  more  water  vapor  in  them. 

It  is  only  on  the  valley  floor  that  any  serious  injury  may  be  caused 
by  low  temperatures  during  the  blooming  period  or  some  time  there¬ 
after.  Even  on  the  valley  floor  where  there  may  be  some  slight  ele¬ 
vations,  no  frosts  occur,  when  serious  injury  may  result  even  a  few 
feet  below.  The  hillsides  surrounding  the  valley  usually  escape  frost 
altogether.  However,  it  is  on  the  valley  floor  that  many  of  the  most 
profitable  orchards  are  found;  hence  the  necessity  of  preventing 
frost  injury.  It  has  been  found  that  the  temperature  2  to  3  feet 
from  the  ground  may  often  register  several  degrees  below  tempera¬ 
tures  taken  at  higher  elevations.  For  instance,  the  writer  has  noted 
a  difference  of  6  degrees  between  two  thermometers,  one  being  about 
4  feet  from  the  ground  and  the  other  only  IS  inches  above  it.  Since 
freezing  temperatures  occur  simply  by  the  cold  air  settling  in  the 
lower  spots  in  the  valley  when  the  air  is  perfectly  calm,  it  is  evident 
that  this  is  the  most  favorable  time  for  maintaining  fires  or  smudges 
in  the  orchard.  High  winds  never  occur  during  the  time  that  the 
temperature  may  be  below  the  freezing  point.  It  has  been  previously 
mentioned  that  a  slight  breeze  usually  comes  up  from  the  south  dur¬ 
ing  the  early  morning.  However,  this  breeze  is  never  sufficient  to 
more  than  waft  the  smudge  through  the  orchards  and  does  not  inter¬ 
fere  to  any  great  extent  in  keeping  up  the  temperature  where  fires  are 
built.  It  will  be  seen  that  the  conditions  in  the  valley  are  ideal  foi 
the  prevention  of  injury  from  freezing. 


20 


PROTECTION  OP  ORCHARDS  PROM  SPRING  FROSTS. 


INJURIOUS  TEMPERATURES. 

The  temperatures  at  which  the  principal  orchard  fruits  are  liable  to 
be  injured  by  frost  are  given  in  the  following  table.  Some  of  the 
figures  have  been  taken  from  data  furnished  by  orchardists,  but  the 
greater  part  of  the  table  is  based  on  actual  observations  made  on  the 
Pacific  coast  by  the  writer.  The  temperatures  given  can  not  be  con¬ 
sidered  as  absolute,  since  weather  conditions  previous  to  a  freeze 
determine  to  a  very  great  extent  the  ability  of  plants  to  withstand 
low  temperatures.  A  few  days  of  very  warm  weather,  together  with 
an  ample  supply  of  soil  moisture,  will  cause  the  newly  formed  cells  of 
the  blossoms  and  fruits  to  be  filled  with  a  watery  protoplasm,  or  cell 
sap,  which  freezes  more  readily  than  concentrated  cell  sap.  If  a 
freeze  follows  a  period  of  weather  in  which  temperatures  have  been 
such  as  to  produce  slow  growth,  lower  temperatures  than  those  given 
in  the  table  may  not  cause  injury. 


Table  III. — Temperatures  injurious  to  fruit  when  in  hud ,  in  blossom,  etc.a 


Fruit. 

In  bud. 

In  blos¬ 
som. 

In  set¬ 
ting 
fruit. 

At  other 
times. 

Almonds . 

°  F. 

28 

°  F. 

30 

0  F. 

30 

°  F. 

28 

Apples . . . 

27 

29 

30 

25 

Apricots . 

30 

31 

31 

30 

Cherries . 

29 

30 

30 

29 

Peaches . 

29 

30 

30 

28 

Pears . 

28 

29 

31 

29 

28 

Plums . 

30 

31 

29 

Prunes . 

30 

31 

31 

29 

a  These  temperatures  are  approximately  those  of  the  air  in  contact  with  the  fruits  and  blossoms.  It  is 
quite  possible,  however,  that  very  delicate  measurements  would  indicate  somewhat  lower  temperatures, 
due  to  evaporation  from  the  immediate  surface  of  the  plants. 


RESULTS  OF  THE  WORK. 

In  the  use  of  smudge  fires  where  the  temperature  may  reach  as  low 
as  20°  F.,  the  writer  has  found  that  by  using  fifty  wood  fires  per  acre 
a  temperature  of  28°  to  29°  F.  could  be  maintained  in  the  orchards. 
In  other  words,  the  temperature  could  be  raised  8  or  9  degrees. 
Where  it  was  necessary  to  raise  the  temperature  5  or  6  degrees,  only 
half  as  many  fires  were  required.  A  mixture  of  wood  and  coal  was 
probably  a  trifle  better  than  wood  alone.  Since  the  coal  is  mined 
near  Medford  and  is  not  very  expensive  it  is  probable  that  this  ma¬ 
terial  will  be  in  greater  demand  another  year  should  it  be  necessary 
to  prevent  frost  injury.  Crude  oil  was  used  only  to  a  very  limited 
extent,  for  the  reason  mentioned  before — that  it  did  not  burn  read¬ 
ily.  Where  it  was  used  the  temperature  was  not  raised  more  than  2 
or  3  degrees  when  forty  smudge  pots  were  burned  to  the  acre.  Straw 

401 


PROTECTION  OF  ORCHARDS  FROM  SPRING  FROSTS. 


21 


and  manure,  which  were  used  mostly  as  a  smudge  in  the  morning 
just  before  the  sun  came  up,  were  intended  only  as  a  blanket  to  pre¬ 
vent  the  sun  from  warming  up  the  blossoms  too  quickly.  These 
materials  were  rarely  used  alone,  since  in  most  instances  it  was 
hardly  possible  to  raise  the  temperature  more  than  a  degree  or  two 
with  them.  Where  some  sawdust  which  had  been  saturated  with 
tar  was  used  in  connection  with  the  straw  and  manure,  the  tempera¬ 
ture  was  raised  some  2  or  3  degrees  with  about  forty  fires  to  the 
acre. 

The  difference  between  the  smudged  and  the  unsmudged  orchard,  or 
even  part  of  the  same  orchard  remaining  unsmudged,  was  very  marked. 
In  several  instances  the  orchards  which  had  been  smudged  set  a  full 
crop,  while  in  those  that  were  similarly  situated  and  not  smudged 
the  crop  was  entirely  destroyed.  There  is  certainly  no  doubt  in  the 
writer's  mind  that  had  the  growers  smudged  generally  it  would  have 
required  much  less  work  on  the  part  of  those  who  did  smudge.  For 
instance,  where  an  isolated  orchardist  smudged  and  his  neighbors 
did  not  there  was  a  tendency  for  the  fires  to  produce  an  upward  cur¬ 
rent  of  air,  causing  cold  currents  to  rush  in  and  lower  the  temperature. 

VALUE  OF  FIRING  THE  ORCHARDS  WHEN  THE  COST  IS  COMPARED 

WITH  THE  VALUE  OF  THE  CROP. 


The  writer  has  recorded  several  interesting  statements  from  grow¬ 
ers  who  fired  and  smudged  successfully.  Mr.  W.  H.  Brown  states 
that  with  a  cost  of  about  $6  per  acre  for  the  season  he  was  able  to  save 
10  acres  of  apples,  and  estimates  the  value  of  his  crop  at  $6,000.  The 
previous  year  one  freeze  which  occurred  on  May  5  destroyed  his  entire 


crop. 

Mr.  G.  E.  Marshall  makes  the  following  statement:  “The  entire 
quantity  of  material  used  for  the  season  was  5  pounds  ol  crude  oil 
(used  principally  in  saturating  shavings  and  other  material),  1,000 
old  rails,  300  old  stumps,  1  ton  of  waste  bitumen,  3  tons  o!  coal,  800 
large  bundles  of  tree  primings,  25  loads  of  manure,  and  3  loads  ol 
planing-mill  shavings.  With  this  material  I  saved  the  crop  on  9 
acres  of  Yellow  Newtown,  7  acres  of  Monmouth  (Red  (  heck  1  ippin), 
and  about  2  acres  of  Jonathan  apples,  also  6  acres  ol  T\  inter  Nebs  a  u<l 
3  acres  each  of  Anjou  and  Bartlett  pears  (total,  30  acres).  1  did  not 
smudge  3  acres  of  Cornice  pears  and  they  were  mostly  killed.  Mi. 
Marshall  does  not  state  the  value  of  his  crop  per  acre,  but  it  is  doubt¬ 
less  no  less  than  that  of  Mr.  Brown's. 

Mr.  James  W.  Myers  makes  the  statement  that  with  a  total  cost  of 

about  $15  per  acre  he  was  able  to  save  his  crop  of  apples,  lb  <  M1 
mates  that  had  he  not  smudged,  at  least  two-thirds  ol  the  <  h>|>  "(U|1  ^ 
have  been  lost.  The  crop  in  this  orchard  has  brought  as 


401 


22 


PROTECTION  OF  ORCHARDS  FROM  SPRING  FROSTS. 


$1,000  per  acre,  and  from  all  appearances  the  same  price  will  be 
equaled  this  year.  A  number  of  similar  statements  from  other 
growers  who  were  just  as  successful  might  be  given. 

It  is  quite  possible  that  in  many  cases  some  of  the  growers  fired  and 
smudged  more  frequently  than  was  really  necessary.  This  was  done 
early  in  the  season  before  they  felt  confident  that  weather  conditions 
could  be  pretty  accurately  predicted.  At  no  time  during  the  season 
did  the  writer  fail  to  predict  frost  to  within  a  degree  or  two  of  what 
actually  occurred.  The  hour  at  which  firing  would  be  necessary  was 
also  given  out.  Another  year,  with  a  well-equipped  station  and  a 
competent  and  zealous  observer  in  charge,  in  whom  the  growers 
would  have  confidence,  the  cost  of  smudging  might  be  considerably 
reduced  should  it  be  found  necessarv  to  make  use  of  it. 

4/ 

PRACTICAL  SUGGESTIONS  ON  THE  USE  OF  THE  PSYCHROMETER 
AND  OTHER  METEOROLOGICAL  INSTRUMENTS. 

Wherever  it  is  found  necessary  to  protect  orchards  from  frost 
injury,  each  fruit  grower  should  provide  himself  with  the  following 
apparatus : 

(1)  A  psychrometer  with  tables  for  determining  dew-point  tem¬ 
peratures.  This  instrument  may  be  purchased  from  a  number  of 
reliable  concerns  in  the  United  States  for  from  $4  to  $5. 

Although  it  is  advisable  to  purchase  a  high-grade  instrument  for 
making  dew-point  determinations,  a  very  serviceable  instrument  may 
be  made  by  the  average  person  at  a  very  moderate  cost.  An  illustra¬ 
tion  of  this  instrument  is  shown  as  figure  10.  Procure  two  fairly  good 
thermometers  of  the  kind  with  the  scale  marked  on  a  strip  of  metal 
which  is  attached  to  the  tube  by  means  of  small  wire  clamps.  The 
bulb  and  scale  are  removable  from  the  tin  protective  shield.  Slide 
one  of  the  thermometers  with  its  attached  scale  downward  so  that 
the  bulb  projects  below  the  lower  end  of  the  frame.  Fix  the  ther¬ 
mometers  in  the  frame  so  that  they  will  not  slide  out  when  the 
instrument  is  whirled.  This  may  be  done  by  drilling  small  holes 
through  the  frame  and  scale  and  binding  the  two  together  with  wire. 
The  two  thermometers  are  now  fixed  together  back  to  back  by  soldering 
or  by  small  rivets,  as  illustrated  in  figure  11.  A  piece  of  heavy  wire 
bent  in  the  form  of  a  U  should  be  soldered  to  the  lower  end  of  the 
wet-bulb  frame  as  a  protection  against  accidental  breakage.  The  pro¬ 
jecting  bulb  must  now  be  covered  with  thin  muslin  cloth.  A  string  or 
leather  thong  about  2  feet  long  should  be  tied  in  the  rings,  which  are 
soldered  to  the  top  of  the  instrument.  This  string  serves  as  a  means 
with  which  to  whirl  the  thermometers.  After  using  the  psychrometer 
a  few  times  the  linen  cloth  should  bo  changed. 

o 


401 


PROTECTION  OF  ORCHARDS  FROM  SPRING  FROSTS. 


23 


In  using  the  instrument,  wet  the  covered  bulb  and  whirl  it  rapidly 
so  that  evaporation  will  take  place  from  the  wet  surface.  The  whirl¬ 
ing  should  be  continued  until  the  mercury  is  brought  as  low  as  pos¬ 
sible.  When  it  can  not  be  lowered  any  farther  it  should  be  read 
simultaneously  with  the  dry-bulb  thermometer.  The  temperature 
of  the  dry  bulb,  which  is  the  air  temperature,  and  the  difference 
between  it  and  that  of  the  wet  bulb  should  then  be  referred  to  Table 
II.  It  is  best  when  using  the  psychrometer  to  take  several  readings 
and  then  take  the  mean  before  referring  to  the  table.  In  this  way 
greater  accuracy  will  result.  One  point  which  should  not  be  over¬ 
looked  in  the  matter  of  selecting  the  thermometers  is  that  the  two 
instruments  should  read  exactly  alike  for  all  temperatures,  because 
it  is  the  difference  between  the  two  thermometers  that  is  of  the 
greatest  importance. 

(2)  Several  good  thermometers,  which  should  be  placed  at  different 
points  in  the  orchard  at  an  elevation  of  from  4  to  5  feet  from  the 
ground.  Temperatures  near  the  ground  are  always  much  lower  than 
those  at  4  or  5  feet  higher.  It  is  the  temperature  of  the  air  which 
surrounds  the  fruiting  portion  of  the  tree  that  we  wish  to  know  about. 

(3)  A  maximum  and  minimum  thermometer.  This  instrument 
is  not  absolutely  necessary,  but  it  is  very  useful  in  serving  as  a  check 
upon  the  observations  made  with  the  other  thermometers. 

(4)  An  aneroid  barometer.  This  instrument  is  rather  costly,  being 
worth  from  $18  to  $20,  but  if  a  single  grower  does  not  desire  to  buy 
one,  several  might  purchase  the  instrument  together.  This  instru¬ 
ment  indicates  the  air  pressure  and  the  highs  and  lows  which  may  be 
seen  marked  on  the  weather  maps.  During  a  period  of  high  pressure 
the  chances  are  that  frosts  may  bo  expected,  while  during  low  pres¬ 
sure,  which  means  that  there  is  a  considerable  quantity  of  water 


vapor  in  the  atmosphere,  frosts  are  not  so  likely  to  appear.  I  Ins 
instrument  would  indicate  the  movement  of  the  high  and  low  pressure 
of  the  atmosphere  and  act  as  a  check  upon  the  psychrometer  obser¬ 
vations. 

(5)  It  would  also  be  well  to  get  the  daily  weather  maps  and  warn¬ 
ings  from  the  nearest  weather  stations.  these  reports  would  indi¬ 
cate,  at  least  in  a  general  way,  the  kind  of  weather  that  would  be 
likely  to  occur  within  a  certain  time  and  would  give  this  information 
long  enough  in  advance  so  that  preparation  might  be  made  for  fning 
in  the  orchards.  For  very  small  orchards  preparation  may  be  quick h 
made,  but  where  the  tracts  are  large  it  requires  some  time.  A  ithout 
doubt  the  small  tracts  of,  say,  10  acres  or  less  can  be  much  nioie  ea>il\ 

and  successfully  handled. 

401 


24 


PROTECTION  OF  ORCHARDS  FROM  SPRING  FROSTS. 


CONCLUSIONS. 

(1)  There  is  no  doubt  that  frost  injury  may  be  prevented  by  the 
use  of  fires  and  smudges. 

(2)  Wood  and  coal  have  proved  to  be  the  best  fuel. 

(3)  Where  the  temperature  drops  to  20°  F.  it  would  seem  that 
fifty  fires  per  acre  are  necessary.  Only  half  as  many  are  needed  when 
the  temperature  reaches,  say,  25  to  26°  F. 

(4)  Shavings,  chips,  or  other  fine  material  in  paper  sacks  saturated 
with  crude  oil  or  kerosene  have  been  found  best  for  starting  the  fires 
quickly.  Kerosene  torches  for  lighting  the  fires  have  also  proved  to 
be  very  serviceable  as  compared  with  matches. 

(5)  Straw  and  stable  manure  are  valuable  for  producing  dense 
smudges,  but  are  not  effective  in  raising  the  temperature  in  the 
orchard.  The  value  of  the  smudge,  or  dense  smoke,  is  more  to  pro¬ 
tect  the  trees  from  the  early  morning  sun  where  some  slight  freezing 
of  the  blossoms  and  the  fruit  has  occurred  during  the  night. 

(6)  The  cost  of  firing  with  wood  and  coal,  including  labor,  should 
not  average  more  than  $3  a  night  per  acre,  even  where  it  may  be 
necessary  to  keep  the  fires  burning  five  or  six  hours.  In  some  locali¬ 
ties  where  wood  can  be  had  without  expense  except  for  the  hauling, 
these  figures  might  be  reduced  somewhat.  However,  in  localities 
where  wood  is  rather  scarce  they  would  probably  be  somewhat  higher. 

(7)  The  results  of  the  past  season’s  work  in  the  Rogue  River  Valley 
have  shown  that  many  acres  of  crops  valued  at  from  $500  to  $1,000 
per  acre  have  been  saved  at  a  total  expenditure  of  not  more  than  $15 
to  $20  per  acre  for  firing.  Very  striking  examples  have  been  seen 
where  unsmudged  orchards  adjoining  those  that  have  been  smudged 
have  borne  no  fruit. 


[A  list  giving  the  titles  of  all  Farmers’  Bulletins  available  for  distribution  will  be 
sent  free  upon  application  to  any  Member  of  Congress  or  the  Secretary  of  Agriculture.] 
401 


o 


